V2x message sending method, apparatus, and system

ABSTRACT

Embodiments of the present invention provide a V2X message sending method, apparatus, and system, and relate to the field of Internet of Vehicles. The method includes: obtaining, by a terminal, first configuration information, where the first configuration information is used for determining a first transmission resource pool; determining the first transmission resource pool based on the first configuration information; selecting a first transmission resource from the first transmission resource pool in a first transmission resource obtaining manner when a preset condition is met; and sending a V2X message by using the first transmission resource.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/264,229, filed on Jan. 31, 2019, which is a continuation ofInternational Application No. PCT/CN2016/094242, filed on Aug. 9, 2016,the disclosure of which is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

Embodiments of the present invention relate to the field of Internet ofVehicles, and in particular, to a V2X message sending method, apparatus,and system.

BACKGROUND

In an Intelligent Transportation System (ITS), various types ofinformation related to transportation are obtained in a timely mannerthrough vehicle to vehicle (V2V) communication, vehicle toinfrastructure (V2I) communication, vehicle-to-pedestrian (V2P)communication, or vehicle-to-network (V2N) communication. Thesecommunication manners may be collectively referred to as vehicle to X(V2X) communication. X is a collective term for vehicles, roadinfrastructure, pedestrians, and networks.

When a V2X message is transmitted using a Long Term Evolution (LTE)technology, two user equipments (UEs) may be directly connected to eachother for communication. When the two UEs are directly connected to eachother for communication, an eNB first configures a transmission resourcepool for a UE. The UE selects a transmission resource in an idle statefrom the transmission resource pool in a manner in which a transmissionresource is selected after channel sensing is performed. Then, the UEsends the V2X message by using the transmission resource in the idlestate. The manner in which a transmission resource is selected afterchannel sensing is performed is as follows. The UE senses eachtransmission resource in the transmission resource pool, where a typicalvalue of sensing duration is 1000 ms; and then determines thetransmission resource in the idle state based on a sensing result.

In the foregoing manner, the transmission resource in the idle state canbe selected only after at least 1000-ms sensing duration. Therefore, themanner is not applicable to all V2X message sending scenarios. In somespecific sending scenarios, for example, after the UE initially obtainsconfiguration information of the transmission resource pool, even thoughthere is a to-be-transmitted V2X message, the UE needs to wait for the1000-ms sensing duration, and then select the transmission resource inthe idle state to send the V2X message. Because a transmission delay ofthe V2X message is 100 ms or 20 ms, the UE may fail to send the V2Xmessage after waiting for the 1000-ms sensing duration.

SUMMARY

To resolve a problem with the current system that a manner of selectinga transmission resource cannot be applied to all V2X message sendingscenarios, and V2X message sending may fail in a specific sendingscenario, embodiments of the present invention provide a V2X messagesending method, apparatus, and system. The technical solutions are asfollows:

According to a first aspect of the embodiments of the present invention,a V2X message sending method is provided. The method includes obtaining,by a terminal, first configuration information. The first configurationinformation is used for determining a first transmission resource pool.The method further includes determining, by the terminal, the firsttransmission resource pool based on the first configuration information.The method further includes selecting, by the terminal, a firsttransmission resource from the first transmission resource pool in thefirst transmission resource obtaining manner when determining that apreset condition is met. The method further includes sending a V2Xmessage by using the first transmission resource.

In this design, it can be ensured that the V2X message is normallytransmitted in a specific sending scenario when the preset condition ismet.

In a possible design, the specific sending scenario is a scenario inwhich cell handover is performed on the terminal, and the obtaining, bya terminal, first configuration information includes receiving, by theterminal, radio resource control (RRC) dedicated signaling sent by afirst access network device; and obtaining, by the terminal, cellhandover configuration information and the first configurationinformation from the RRC dedicated signaling. The cell handoverconfiguration information and the first configuration information areconfigured by a second access network device. After the obtaining, by aterminal, first configuration information, the method further includeshanding over the terminal from a source cell to a target cell based onthe cell handover configuration information. The first access networkdevice is an access network device corresponding to the source cell, andthe second access network device is an access network devicecorresponding to the target cell.

In a possible design, the preset condition includes a current momentbelongs to a handover time period, a start time of the handover timeperiod is a time at which the RRC dedicated signaling is received, andan end time of the handover time period is a time at which the terminalis handed over to the target cell.

In this implementation, it can be ensured that the V2X message isnormally transmitted in a cell handover scenario.

In a possible design, before the selecting, by the terminal, atransmission resource from the first transmission resource pool in afirst transmission resource obtaining manner when determining that apreset condition is met. The method further includes obtaining, by theterminal, second configuration information. The second configurationinformation is used for determining a second transmission resource pool,a manner of obtaining a transmission resource from the secondtransmission resource pool is a second transmission resource obtainingmanner. The second transmission resource obtaining manner is atransmission resource obtaining manner in which a transmission resourceis selected after channel sensing is performed for sensing duration T2.The method further includes determining, by the terminal, the secondtransmission resource pool based on the second configurationinformation.

In a possible design, the preset condition includes at least one of thefollowing conditions: no valid sensing result is obtained from thesecond transmission resource pool; sensing duration in the secondtransmission resource pool is less than T2; after the secondconfiguration information is updated, sensing duration in the secondtransmission resource pool is less than T2; synchronization between theterminal and the access network device becomes invalid; after asynchronization source is updated, sensing duration in the secondtransmission resource pool is less than T2 based on a clock of anupdated synchronization source; a difference between a time at which theV2X message is generated and a time at which the second configurationinformation is obtained is less than a preset threshold; or notransmission resource in an idle state is sensed in the secondtransmission resource pool.

In this implementation, it can be ensured that the V2X message isnormally transmitted in a scenario in which no valid sensing result isobtained from the second transmission resource pool.

In a possible design, the method further includes when obtaining a validsensing result from the second transmission resource pool, obtaining, bythe terminal, a second transmission resource from the secondtransmission resource pool in the transmission resource obtaining mannerin which a transmission resource is selected after channel sensing isperformed for sensing duration T2, and sending the V2X message by usingthe second transmission resource.

In a possible design, the first transmission resource pool and thesecond transmission resource pool are a same resource pool, and thefirst transmission resource obtaining manner is different from thesecond transmission resource obtaining manner.

In a possible design, the obtaining, by a terminal, first configurationinformation includes: obtaining, by the terminal, the preconfiguredfirst configuration information; receiving, by the terminal, radioresource control RRC dedicated signaling sent by the access networkdevice, and obtaining the first configuration information from the RRCdedicated signaling; or receiving, by the terminal, system informationsent by the access network device, and obtaining the first configurationinformation from the system information.

In a possible design, the first transmission resource obtaining mannerincludes at least one of the following manners: a random selectionmanner; a manner in which a transmission resource is selected afterchannel sensing is performed for sensing duration T1, where the sensingduration T1 is less than a transmission delay value of the V2X message;or a carrier sense multiple access with collision avoidance CSMA/CAmanner.

According to a second aspect of the embodiments of the presentinvention, a V2X message sending method is provided, and the methodincludes: sending, by an access network device, first configurationinformation to a terminal, where the first configuration information isused for determining a first transmission resource pool. The terminal isconfigured to: determine the first transmission resource pool based onthe first configuration information; when determining that a presetcondition is met, select a first transmission resource from the firsttransmission resource pool in a first transmission resource obtainingmanner; and send a V2X message by using the first transmission resource.

In a possible design, the access network device is a first accessnetwork device, and the first access network device is an access networkdevice corresponding to a source cell. The sending, by an access networkdevice, first configuration information to a terminal includes: whencell handover needs to be performed on the terminal, sending, by thefirst access network device, a handover request message to a secondaccess network device, where the second access network device is anaccess network device corresponding to a target cell. The sendingfurther includes receiving, by the first access network device, ahandover acknowledgement message sent by the second access networkdevice, where the handover acknowledgement message includes cellhandover configuration information and the first configurationinformation. The sending further includes sending, by the first accessnetwork device, RRC dedicated signaling to the terminal, where the RRCdedicated signaling includes the cell handover configuration informationand the first configuration information. The terminal is configured to:be handed over from the source cell to the target cell based on the cellhandover configuration information, select the first transmissionresource from the first transmission resource pool in the firsttransmission resource obtaining manner within a handover time period,and send the V2X message by using the first transmission resource.

In a possible design, the method further includes: sending, by the firstaccess network device, second configuration information to the terminal,where the second configuration information is used for configuring asecond transmission resource pool. A second transmission resourceobtaining manner is used for the second transmission resource pool, andthe second transmission resource obtaining manner is a transmissionresource obtaining manner in which a transmission resource is selectedafter channel sensing is performed for sensing duration T2.

In a possible design, the method further includes sending, by the accessnetwork device, RRC dedicated signaling to the terminal, where the RRCdedicated signaling carries the first configuration information.Alternatively, the method includes sending, by the access networkdevice, system information (SI) to the terminal, where the systeminformation carries the first configuration information.

According to a third aspect of the embodiments of the present invention,a message sending method is provided. The method includes receiving, bya second access network device, a handover request message sent by afirst access network device, where the handover request message is sentby the first access network device when cell handover needs to beperformed on a terminal, and the first access network device is anaccess network device corresponding to a source cell. The methodincludes sending, by the second access network device, a handoverrequest response message to the first access network device, where thehandover request response message carries cell handover configurationinformation and first configuration information. The method includes thefirst access network device is configured to send RRC dedicatedsignaling to the terminal, where the RRC dedicated signaling includesthe cell handover configuration information and the first configurationinformation. The terminal is configured to: be handed over from thesource cell to a target cell based on the cell handover configurationinformation, select a first transmission resource from the firsttransmission resource pool in the first transmission resource obtainingmanner within a handover time period, and send a V2X message by usingthe first transmission resource.

In a possible design, the first transmission resource obtaining mannerincludes any one of the following manners: a random selection manner; amanner in which a transmission resource is selected after channelsensing is performed for sensing duration T1, where the sensing durationT1 is less than a transmission delay value of the V2X message; or acarrier sense multiple access with collision avoidance CSMA/CA manner.

According to a fourth aspect, an embodiment of the present inventionprovides a V2X message sending apparatus. The message sending apparatusincludes at least one unit, and the at least one unit is configured toimplement the V2X message sending method provided in any one of thefirst aspect or the possible implementations of the first aspect.

According to a fifth aspect, an embodiment of the present inventionprovides a V2X message sending apparatus. The message sending apparatusincludes at least one unit, and the at least one unit is configured toimplement the V2X message sending method provided in any one of thesecond aspect or the possible implementations of the second aspect.

According to a sixth aspect, an embodiment of the present inventionprovides a V2X message sending apparatus. The message sending apparatusincludes at least one unit, and the at least one unit is configured toimplement the V2X message sending method provided in any one of thethird aspect or the possible implementations of the third aspect.

According to a seventh aspect, an embodiment of the present inventionprovides a terminal. The terminal includes a processor and a memory. Theprocessor is configured to store one or more instructions. Theinstructions are instructed to be executed by the processor. Theprocessor is configured to implement the message sending method providedin any one of the first aspect or the possible implementations of thefirst aspect.

According to an eighth aspect, an embodiment of the present inventionprovides an access network device. The access network device includes atleast one unit, and the at least one unit is configured to implement theV2X message sending method provided in any one of the second aspect orthe possible implementations of the second aspect.

According to a ninth aspect, an embodiment of the present inventionprovides a second access network device. The second access networkdevice includes at least one unit, and the at least one unit isconfigured to implement the V2X message sending method provided in anyone of the third aspect or the possible implementations of the thirdaspect.

According to a tenth aspect, an embodiment of the present inventionprovides a computer readable storage medium. The computer readablestorage medium stores an executable program used for implementing theV2X message sending method provided in any one of the first aspect orthe possible designs of the first aspect.

According to an eleventh aspect, an embodiment of the present inventionprovides a computer readable storage medium. The computer readablestorage medium stores an executable program used for implementing theV2X message sending method provided in any one of the second aspect orthe possible designs of the second aspect.

According to a twelfth aspect, an embodiment of the present inventionprovides a computer readable storage medium. The computer readablestorage medium stores an executable program used for implementing theV2X message sending method provided in any one of the third aspect orthe possible designs of the third aspect.

According to a thirteenth aspect, a V2X message sending system isprovided. The V2X message sending system includes a terminal and anaccess network device. The terminal includes the V2X message sendingapparatus provided in any one of the fourth aspect or the possibledesigns of the fourth aspect, and the access network device includes theV2X message sending apparatus provided in any one of the fifth aspect orthe possible designs of the fifth aspect.

According to a fourteenth aspect, a V2X message sending system isprovided. The message sending system includes a terminal and an accessnetwork device. The terminal includes the message sending apparatusprovided in any one of the seventh aspect or the possible designs of theseventh aspect, and the access network device includes the V2X messagesending apparatus provided in any one of the eighth aspect or thepossible designs of the eighth aspect.

According to a fifteenth aspect, a V2X message sending system isprovided. The V2X message sending system includes a terminal, a firstaccess network device, and a second access network device. The terminalincludes the V2X message sending apparatus provided in any one of thefourth aspect or the possible designs of the fourth aspect, the firstaccess network device includes the V2X message sending apparatusprovided in any one of the fifth aspect or the possible designs of thefifth aspect, and the second access network device includes the V2Xmessage sending apparatus provided in any one of the fifth aspect or thepossible designs of the fifth aspect.

According to a sixteenth aspect, a V2X message sending system isprovided. The V2X message sending system includes a terminal, a firstaccess network device, and a second access network device. The terminalincludes the terminal provided in any one of the seventh aspect or thepossible designs of the seventh aspect, the first access network deviceincludes the access network device provided in any one of the eighthaspect or the possible designs of the eighth aspect, and the secondaccess network device includes the second access network device providedin any one of the ninth aspect or the possible designs of the ninthaspect.

The technical solutions provided in the embodiments of the presentinvention have at least the following beneficial effects.

When determining that the preset condition is met, the terminal selectsthe first transmission resource from the first transmission resourcepool in the first transmission resource obtaining manner, to send theV2X message. Duration spent in selecting the transmission resource inthe first transmission resource obtaining manner is less than atransmission delay of the V2X message. Therefore, it can be ensured thatthe V2X message can be normally transmitted in a specific sendingscenario when the preset condition is met.

BRIEF DESCRIPTION OF THE DRAWINGS

The following briefly describes the accompanying drawings required fordescribing the embodiments. Apparently, the accompanying drawings in thefollowing descriptions show merely some embodiments of the presentinvention, and a person of ordinary skill in the art may still deriveother drawings from these accompanying drawings without creativeefforts.

FIG. 1 is a schematic structural diagram of a V2X message sending systemaccording to an embodiment of the present invention;

FIG. 2 is a flowchart of a V2X message sending method according to anembodiment of the present invention;

FIG. 3 is a schematic diagram of a principle of a V2X message sendingmethod according to another embodiment of the present invention;

FIG. 4 is a flowchart of a V2X message sending method according toanother embodiment of the present invention;

FIG. 5 is a schematic diagram of a principle of a V2X message sendingmethod according to another embodiment of the present invention;

FIG. 6 is a flowchart of a V2X message sending method according toanother embodiment of the present invention;

FIG. 7 is a block diagram of a V2X message sending apparatus accordingto an embodiment of the present invention;

FIG. 8 is a block diagram of a V2X message sending apparatus accordingto another embodiment of the present invention; and

FIG. 9 is a block diagram of a V2X message sending apparatus accordingto another embodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following further describes the embodiments of the present inventionin detail with reference to the accompanying drawings.

A “module” mentioned in this specification is a program or aninstruction that is stored in a memory and can implement some functions.A “unit” mentioned in this specification is a functional structuredivided based on logic. The “unit” may be implemented by only hardware,or implemented by a combination of software and hardware.

“A plurality” mentioned in this specification means at least two.“And/or” describes an association relationship between associatedobjects and represents that three relationships may exist. For example,A and/or B may represent the following three cases: Only A exists, bothA and B exist, and only B exists. The character “/” usually indicates an“or” relationship between the associated objects.

FIG. 1 is a schematic structural diagram of a message sending system 100according to an embodiment of the present invention. The message sendingsystem 100 includes at least one terminal 120 and at least one accessnetwork device 140.

The terminal 120 is a terminal in the Internet of Vehicles. Optionally,the terminal 120 is at least one of a communications device disposed ina vehicle, a communications device disposed in roadside infrastructure,or a communications device used by a pedestrian. Specifically, theterminal 120 may be a device such as a personal communications service(PCS) phone, a cordless telephone set, a Session Initiation Protocol(SIP) phone, a wireless local loop (WLL) station, or a personal digitalassistant (PDA). The terminal may also be referred to as a system, asubscriber unit, a subscriber station, a mobile station, a mobile, aremote station, an access point, a remote terminal, an access terminal,a user terminal, a user agent, a user device, or user equipment.

The terminal 120 communicates with one or more access network devices140 by using a radio access network (RAN).

The access network device 140 may be a base station, and serves as arouter between the terminal 120 and a remaining part of the accessnetwork, and the remaining part of the access network may include anInternet Protocol (IP) network. The base station may further coordinateattribute management of an air interface. For example, the base stationmay be a base transceiver station (BTS) in GSM or CDMA, or may be aNodeB in WCDMA, or may be an evolved NodeB (eNB or e-NodeB) in LTE. Thisis not limited in this application. An example in which the accessnetwork device 140 is the eNB is used for description in the followingembodiment.

When V2X communication is implemented between two terminals 120, a firstcommunication manner is as follows: A V2X message sent by one terminal120 is sent to the other terminal 120 through forwarding by the accessnetwork device 14 o; and a second communication manner is as follows:The two terminals 120 are directly connected to each other forcommunication. In this embodiment of the present invention, a case inwhich the two terminals 120 are directly connected to each other forcommunication is mainly involved.

When the two terminals 120 are directly connected to each other forcommunication, the access network device 140 preconfigures atransmission resource pool for the terminal 120. The terminal 120selects a transmission resource in an idle state from the transmissionresource pool, and sends the V2X message by using the transmissionresource in the idle state.

The V2X message includes at least one of a V2V message, a V2I message, aV2P message, or a V2N message. Optionally, the V2X message is a messagecarrying V2X data, or the V2X message is V2X data.

FIG. 2 is a method flowchart of a message sending method according to anembodiment of the present invention. An example in which the messagesending method is applied to the terminal 120 shown in FIG. 1 is usedfor description in this embodiment. The method includes the followingsteps.

Step 201: Obtain first configuration information, where the firstconfiguration information is used for determining a first transmissionresource pool.

Optionally, the first configuration information is configured by anaccess network device for the terminal. That is, the terminal receivesRRC dedicated signaling sent by the access network device, and obtainsthe first configuration information from the RRC dedicated signaling; orthe terminal receives system information sent by the access networkdevice, and obtains the first configuration information from the systeminformation. The system information is broadcast information sent by theaccess network device.

Optionally, the first configuration information is the preconfiguredfirst configuration information. To be specific, the first configurationinformation is configuration information that is pre-specified accordingto a communications protocol related to LTE and that is pre-stored inthe terminal. When the first configuration information is thepreconfigured first configuration information, the terminal reads thefirst configuration information stored in the terminal.

Step 202: Determine the first transmission resource pool based on thefirst configuration information.

Step 203: When a preset condition is met, select a first transmissionresource from the first transmission resource pool in a firsttransmission resource obtaining manner.

Optionally, the preset condition is a condition set based on a specificsending scenario. The specific sending scenario is a scenario in which atransmission resource is selected in a manner in which a transmissionresource is selected after channel sensing is performed for sensingduration T2 (where a typical value is 1000 ms); and consequently, V2Xmessage sending fails, or a transmission delay cannot be met.

Optionally, a time spent in selecting the transmission resource in thefirst transmission resource obtaining manner is less than a transmissiondelay value of a V2X message. Optionally, the transmission delay valueis 100 ms or 20 ms.

3. a carrier sense multiple access with collision avoidance (CSMA/CA)manner.

Step 204: Send a V2X message by using the first transmission resource.

In conclusion, the transmission resource is fast selected in the firsttransmission resource obtaining manner. Therefore, when the presetcondition is met, the first transmission resource is selected from thefirst transmission resource pool in the first transmission resourceobtaining manner, and the V2X message is sent by using the firsttransmission resource, so as to ensure that the V2X message can benormally transmitted in a specific sending scenario when the presetcondition is met.

The foregoing specific sending scenario includes at least two types ofscenarios. The following describes an implementation in a first type ofscenario in the embodiments of the present invention with reference toFIG. 3 and FIG. 4, and describes an implementation in a second type ofscenario in the embodiments of the present invention with reference toFIG. 5 and FIG. 6.

Referring to FIG. 3, an access network device 140 configures a firsttransmission resource pool 32 and a second transmission resource pool 34for a terminal 120. In a first type of specific sending scenario, theterminal 120 sends a V2X message by using a transmission resource in thefirst transmission resource pool 32, and a first transmission resourceobtaining manner with a relatively fast selection speed is used in thefirst transmission resource pool 32. In a common sending scenario, theterminal 120 sends a V2X message by using a transmission resource in thesecond transmission resource pool 34, and a conventional secondtransmission resource obtaining manner, namely, a manner in which atransmission resource is selected after channel sensing is performed forsensing duration T2, is used in the second transmission resource pool34. Optionally, T2=1000 ms.

In this case, a first condition includes: No valid sensing result isobtained from the second transmission resource pool.

FIG. 4 is a flowchart of a message sending method according to anembodiment of the present invention. An example in which the method isapplied to the message sending system shown in FIG. 1 is used fordescription in this embodiment. The method includes the following steps.

Step 401: An access network device sends first configuration informationand second configuration information to a terminal.

The first configuration information is used for determining a firsttransmission resource pool, and a manner of obtaining a transmissionresource from the first transmission resource pool is a firsttransmission resource obtaining manner. Optionally, the firsttransmission resource obtaining manner is a random selection manner, amanner in which a transmission resource is selected after channelsensing is performed for sensing duration T1, or a CSMA/CA manner.

The second configuration information is used for determining a secondtransmission resource pool, and a manner of obtaining a transmissionresource from the second transmission resource pool is a secondtransmission resource obtaining manner. Optionally, the secondtransmission resource pool obtaining manner is a manner in which atransmission resource is selected after channel sensing is performed forsensing duration T2.

A selection speed of selecting a resource in the first transmissionresource obtaining manner is greater than a selection speed of selectinga resource in the second transmission resource obtaining manner.

Optionally, the access network device simultaneously sends the firstconfiguration information and the second configuration information tothe terminal; or the access network device first sends the firstconfiguration information to the terminal, and then sends the secondconfiguration information to the terminal; or the access network devicefirst sends the second configuration information to the terminal, andthen sends the first configuration information to the terminal.

Optionally, the access network device sends the first configurationinformation and/or the second configuration information to the terminalby using radio resource control (RRC) dedicated signaling; or the accessnetwork device sends the first configuration information and/or thesecond configuration information to the terminal by using a systeminformation block (SIB) in system information; or the access networkdevice sends the first configuration information and/or the secondconfiguration information to the terminal in a semi-static configurationmanner, and the semi-static configuration manner is a configurationmanner in which one configuration is valid until next configuration isperformed.

Optionally, this step may be omitted when both the access network deviceand the terminal abide by configuration information that ispre-specified in a communications protocol. The terminal reads aninternal memory, and obtains the preconfigured first configurationinformation and/or the preconfigured second configuration information.

Correspondingly, the terminal receives the first configurationinformation and the second configuration information sent by the accessnetwork device.

Step 402: The terminal determines a first transmission resource poolbased on the first configuration information, and determines a secondtransmission resource pool based on the second configurationinformation.

Optionally, transmission resources in the first transmission resourcepool are completely different from transmission resources in the secondtransmission resource pool; or transmission resources in the firsttransmission resource pool are partially the same as and partiallydifferent from transmission resources in the second transmissionresource pool; or transmission resources in the first transmissionresource pool are completely the same as transmission resources in thesecond transmission resource pool.

When the transmission resources in the first transmission resource poolare completely the same as the transmission resources in the secondtransmission resource pool, the first configuration information and thesecond configuration information are same configuration information.Therefore, the access network device needs to send only one piece ofconfiguration information to the terminal. In addition, the firsttransmission resource pool and the second transmission resource pool areessentially a same transmission resource pool. “First” and “second” areused for description, and are merely used to indicate that differenttransmission resource obtaining manners are used.

An example in which the transmission resources in the first transmissionresource pool are completely different from the transmission resourcesin the second transmission resource pool is used for description in thisembodiment.

Optionally, after determining the second transmission resource poolbased on the second configuration information, the terminal starts tocontinuously sense the transmission resource in the second transmissionresource pool.

Step 403: When determining that a preset condition is met, the terminalselects a first transmission resource from the first transmissionresource pool in a first transmission resource obtaining manner.

Optionally, the preset condition includes at least one of the followingconditions.

1. No valid sensing result is obtained from the second transmissionresource pool.

When sensing duration of the terminal in the second transmissionresource pool reaches 1000 ms, if all transmission resources are in abusy state, there is no transmission resource in an idle state.

2. Sensing duration in the second transmission resource pool is lessthan T2.

When the sensing duration in which the terminal senses the transmissionresource in the second transmission resource pool does not reach T2, theterminal cannot obtain a valid sensing result. Optionally, T2 is 1000ms.

3. After the second configuration information is updated, sensingduration in the second transmission resource pool is less than T2.

After the second configuration information is updated, the terminalneeds to redetermine a second transmission resource pool. When sensingduration in which the terminal senses a transmission resource in theredetermined second transmission resource pool is less than T2, theterminal cannot obtain a valid sensing result.

4. Synchronization between the terminal and the access network devicebecomes invalid.

When the synchronization between the terminal and the access networkdevice becomes invalid, a transmission resource cannot be determined,and consequently, the transmission resource in the second transmissionresource pool cannot be sensed.

5. After a synchronization source is updated, sensing duration in thesecond transmission resource pool is less than T2 based on a clock of anupdated synchronization source.

For example, the terminal continuously searches for a synchronizationsource in a running process. When the terminal finds a newsynchronization source whose priority is higher than a priority of acurrently-used synchronization source, the terminal performssynchronization by using a clock of the synchronization source with ahigher priority. When the sensing duration in which the terminalperforms sensing in the second transmission resource pool based on theclock of the updated synchronization source is less than T2, theterminal cannot obtain a valid sensing result.

6. A difference between a time at which a V2X message is generated and atime at which the second configuration information is obtained is lessthan a preset threshold.

7. No transmission resource in an idle state is sensed in the secondtransmission resource pool.

When sensing duration of the terminal in the second transmissionresource pool reaches 1000 ms, if all transmission resources are in abusy state, there is no transmission resource in an idle state.

When determining that any one of the foregoing preset conditions is met,the terminal selects the first transmission resource from the firsttransmission resource pool in the first transmission resource obtainingmanner.

Step 404: The terminal sends a V2X message by using the firsttransmission resource.

Step 405: When obtaining a valid sensing result from the secondtransmission resource pool, the terminal selects a second transmissionresource from the second transmission resource pool in a secondtransmission resource obtaining manner.

The second transmission resource obtaining manner is a manner in which atransmission resource is selected after channel sensing is performed forsensing duration T2.

Step 406: The terminal sends a V2X message by using the secondtransmission resource.

It should be noted that step 405 and step 406 are parallel with step 403and step 404. When the terminal performs step 403 and step 404, step 405and step 406 may not be performed. When the terminal performs step 405and step 406, step 403 and step 404 may not be performed. Optionally,step 405 and step 406 may be performed before step 403 and step 404.This is not limited in this embodiment.

In conclusion, according to the message sending method provided in thisembodiment, when a transmission resource is selected, a selection speedin the first transmission resource obtaining manner is faster than aselection speed in the second transmission resource obtaining manner.When the preset condition is met, the first transmission resource isselected from the first transmission resource pool in the firsttransmission resource obtaining manner, and the V2X message is sent byusing the first transmission resource. Therefore, it can be ensured thatthe V2X message can be normally transmitted in a scenario in which novalid sensing result is obtained from the second transmission resourcepool.

Referring to FIG. 5, when a terminal is in a second type of specificsending scenario (a cell handover scenario), the terminal selects afirst transmission resource from a first transmission resource pool in afirst transmission resource obtaining manner. It is assumed that whenthe terminal 120 needs to be handed over from a cell provided by a firstaccess network device 142 to a cell provided by a second access networkdevice 144, the second access network device 144 configures a firsttransmission resource pool 52 for the terminal. In a cell handoverprocess, the terminal sends a V2X message by using a first transmissionresource in the first transmission resource pool 52.

FIG. 6 is a flowchart of a message sending method according to anotherembodiment of the present invention. The method includes the followingsteps.

Step 601: When cell handover needs to be performed, a first accessnetwork device sends a handover request message to a second accessnetwork device.

When a terminal is in an RRC_CONNECTED mode (RRC_CONNECTED), theterminal sends a measurement report of a current cell to the firstaccess network device. The first access network device is an accessnetwork device corresponding to a source cell before the handover. Thefirst access network device determines, based on the measurement reportsent by the terminal, whether cell handover needs to be performed on theterminal.

When cell handover needs to be performed on the terminal, the firstaccess network device sends a handover request message to the secondaccess network device. The second access network device is an accessnetwork device corresponding to a target cell after the handover.

Correspondingly, the second access network device receives the handoverrequest message sent by the first access network device.

Optionally, the handover request message may correspond to differentsignaling names in different communications systems.

Step 602: The second access network device generates a handover requestacknowledgement message based on the handover request message.

When receiving the handover request message, the second access networkdevice determines, depending on a current running status, whether toallow the current cell handover. If the current cell handover isallowed, the second access network device reserves a necessary resource,for example, a bearer resource established between the second accessnetwork device and a mobility management entity (MME).

After reserving the necessary resource, the second access network devicegenerates the handover request acknowledgement message, and the handoverrequest acknowledgement message includes cell handover configurationinformation and first configuration information.

The cell handover configuration information is configuration informationrelated to a current cell handover process, and includes but is notlimited to: a physical identifier of the target cell, a cell radionetwork temporary identifier (C-RNTI) of the terminal in the targetcell, a dedicated preamble sequence for accessing the target cell, and asecurity algorithm of the target cell.

The first configuration information is used for determining a firsttransmission resource pool, and a manner of obtaining a transmissionresource from the first transmission resource pool is a firsttransmission resource obtaining manner. Optionally, a time spent inselecting a transmission resource in the first transmission resourceobtaining manner is less than a transmission delay value of a V2Xmessage.

Optionally, the first transmission resource obtaining manner is a randomselection manner, a manner in which a transmission resource is selectedafter channel sensing is performed for sensing duration T1, or a CSMA/CAmanner.

Optionally, the first configuration information may be included in thecell handover configuration information, or the first configurationinformation and the cell handover configuration information are includedin parallel in the handover request acknowledgement message. Aninclusion relationship between the first configuration information andthe cell handover configuration information is not limited.

Step 603: The second access network device sends the handover requestacknowledgement message to the first access network device.

The handover request acknowledgement message carries the cell handoverconfiguration information and the first configuration information.

Correspondingly, the first access network device receives the handoverrequest acknowledgement message sent by the second access networkdevice.

Optionally, the handover request acknowledgement message may correspondto different signaling names in different communications systems.Optionally, the first access network device communicates with the secondaccess network device by using an X2 interface.

Step 604: The first access network device sends RRC dedicated signalingto a terminal, where the RRC dedicated signaling carries cell handoverconfiguration information and first configuration information.

Optionally, the RRC dedicated signaling is RRC connectionreconfiguration signaling.

Optionally, the RRC dedicated signaling includes the cell handoverconfiguration information, and the cell handover configurationinformation includes the first configuration information. That is, thefirst configuration information is used as a sub-information entry inthe cell handover configuration information.

Optionally, the RRC dedicated signaling includes the cell handoverconfiguration information and the first configuration information, andthe cell handover configuration information is parallel with the firstconfiguration information.

Correspondingly, the terminal receives the RRC dedicated signaling sentby the first access network device, and obtains the cell handoverconfiguration information and the first configuration information fromthe RRC dedicated signaling.

Optionally, the first configuration information may be included in thecell handover configuration information, or the first configurationinformation and the cell handover configuration information are includedin parallel in the RRC dedicated signaling. An inclusion relationshipbetween the first configuration information and the cell handoverconfiguration information is not limited.

Optionally, when the terminal receives the RRC dedicated signaling, aT304 timer starts.

Step 605: Perform cell handover on the terminal based on the cellhandover configuration information.

Optionally, after the terminal is successfully handed over to the targetcell, the T304 timer stops.

Step 606: The terminal determines a first transmission resource poolbased on the first configuration information.

Step 607: When a current moment belongs to a handover time period, theterminal selects a first transmission resource from the firsttransmission resource pool in a first transmission resource obtainingmanner.

Optionally, a preset condition includes: The current moment belongs tothe handover time period, a start time of the handover time period is atime at which the RRC dedicated signaling is received, and an end timeof the handover time period is a time at which the terminal is handedover to the second access network device.

Optionally, the end time of the handover time period is a time at whicha cell handover timer stops. For example, the cell handover timer is theT304 timer.

The handover time period may also be considered as a running time periodof the cell handover timer.

When determining that the preset condition is met, the terminal selectsthe first transmission resource from the first transmission resourcepool in the first transmission resource obtaining manner.

The first transmission resource obtaining manner is a random selectionmanner, a manner in which a transmission resource is selected afterchannel sensing is performed for sensing duration T1, or a CSMA/CAmanner.

Step 608: The terminal sends a V2X message by using the firsttransmission resource.

It should be noted that there is no necessary sequence between step 605and step 606. In this embodiment, an example in which step 605 isperformed before step 606 is used only for description. Alternatively,step 605 may be performed after step 606, or step 605 and step 606 aresimultaneously performed. This is not limited in this embodiment.

In conclusion, according to the message sending method provided in thisembodiment, when a transmission resource is selected, a selection speedin the first transmission resource obtaining manner is relatively fast.When the preset condition is met, the first transmission resource isselected from the first transmission resource pool in the firsttransmission resource obtaining manner, and the V2X message is sent byusing the first transmission resource. Therefore, it can be ensured thatthe V2X message can be normally transmitted in a cell handover scenarioof the terminal.

In an optional implementation provided based on the embodiment of FIG.6, the first access network device sends second configurationinformation to the terminal. The terminal determines a secondtransmission resource pool based on the second configurationinformation. When cell handover does not need to be performed, theterminal obtains a second transmission resource from the secondtransmission resource pool in a second transmission resource obtainingmanner, and sends the V2X message by using the second transmissionresource.

In an optional implementation provided based on the embodiment of FIG.6, the terminal reads an internal memory, and obtains preconfiguredsecond configuration information. The terminal determines a secondtransmission resource pool based on the second configurationinformation. When cell handover does not need to be performed, theterminal obtains a second transmission resource from the secondtransmission resource pool in a second transmission resource obtainingmanner, and sends the V2X message by using the second transmissionresource.

With reference to the foregoing method embodiments:

Optionally, the random selection manner is as follows. The terminalrandomly selects some transmission resources from n transmissionresources in the first transmission resource pool as the firsttransmission resources. Optionally, a specific quantity of sometransmission resources is dynamically determined by a data volume of ato-be-sent V2X message.

Optionally, the manner in which a transmission resource is selectedafter channel sensing is performed for sensing duration T1 is asfollows. The terminal continuously senses n transmission resources inthe second transmission resource pool, and duration of the continuoussensing is at least T1; and the terminal determines, based on a resultof the continuous sensing, a transmission resource in an idle state.

Optionally, the manner in which a transmission resource is selectedafter channel sensing is performed for sensing duration T2 is asfollows. The terminal continuously senses n transmission resources inthe first transmission resource pool, and duration of the continuoussensing is at least T2; and the terminal determines, based on a resultof the continuous sensing, a transmission resource in an idle state. Forexample, T2 is less than T1.

Optionally, the continuous sensing is as follows. The terminal detectssignal energy received on the n transmission resources; and when thesignal energy is greater than a threshold, determines that thetransmission resource is in a busy state; or when the signal energy isless than a threshold, determines that the transmission resource is inan idle state. Alternatively, the continuous sensing is as follows. Theterminal decodes a signal that is received on the n transmissionresources; and when valid information is obtained through decoding,determines that the transmission resource is in a busy state; or when novalid information is obtained through decoding, determines that thetransmission resource is in an idle state. Optionally, transmissionresources are divided in a unit of a resource block; or divided in aunit of a subframe; or divided in a unit of m symbols, where m=1, 2, 3,or 4.

Optionally, for the CSMA/CA manner, refer to the 802.11 protocolstandard formulated by the Institute of Electrical and ElectronicsEngineers (IEEE).

Optionally, the transmission resource in the foregoing embodiments isalso referred to as a time-frequency resource. The time-frequencyresource includes a time domain resource and a frequency domainresource.

Optionally, for a manner in which a transmission resource is selectedafter channel sensing is performed for sensing duration T1 or T2, atransmission resource is selected from a transmission resource poolbased on service priority information. Specifically, when the V2Xmessage enters a logical channel of an access layer, the logical channelhas a corresponding service priority. The service priority may beobtained by using a corresponding primitive of the V2X message, or maybe obtained through configuration or preconfiguration by a base station.Optionally, V2X messages with different service priorities may enterdifferent logical channels. A media access control (MAC) layerdetermines a first transmission priority based on a service priority ofa logical channel having a V2X service, and notifies a physical layer ofthe first transmission priority. The physical layer determines a validtransmission resource set based on the first transmission priority andthe result of the continuous sensing, and notifies the MAC layer of thevalid transmission resource set, so that the MAC layer determines, basedon the valid transmission resource set, a transmission resource used forsending the V2X service.

Optionally, when the V2X service is transmitted, a MAC layer of asending terminal sends, to a physical layer, a second transmissionpriority and a media access control protocol data unit (MAC PDU) inwhich the V2X service is encapsulated, so that the physical layerencapsulates the second transmission priority in an schedulingassignment (SA) corresponding to the MAC PDU and sends the SA. Afterreceiving the SA, a physical layer of a nearby receiving terminaldetermines a service priority of the MAC PDU based on the secondtransmission priority obtained through decoding. Optionally, the secondtransmission priority is a highest service priority in servicepriorities corresponding to all logical channel data encapsulated in theMAC PDU.

Optionally, for the sending terminal, the first transmission priority isequal to the second transmission priority.

Optionally, the MAC PDU used for transmitting the V2X service on adirect link uses a first transmission format. Specifically, a header ofthe MAC PDU carries a source address and a target address. A length ofbits occupied by the source address of the MAC PDU is equal to a lengthof bits occupied by the target address of the MAC PDU. Typically, thebits are 24 bits. Optionally, the MAC PDU needs to carry first formatindication information. The first format indication information is usedto notify the receiving terminal that the MAC PDU uses the firsttransmission format. Optionally, the SA used for transmitting the V2Xservice on a direct link uses a second transmission format.Specifically, the SA does not carry a truncated destination address.Optionally, the SA needs to carry second format indication information.The second format indication information is used to notify the receivingterminal that the SA uses the second transmission format.

Optionally, the time domain resource is a symbol, a symbol group, atimeslot (slot), or a subframe. The timeslot is a 0.5-ms timeslot in anLTE system with 15-kHz subcarrier spacing, or a timeslot in acommunications system with larger subcarrier spacing. The subframe is a1-ms subframe in an LTE system with 15-kHz subcarrier spacing, or asubframe in a communications system with larger subcarrier spacing. Thisis not limited in this embodiment.

Optionally, the frequency domain resource is a PRB, a physical resourceblock group (RBG), a virtual resource block (VRB), a subcarrier, or asubcarrier group. The PRB and the VRB are basic units for resourceallocation in different meanings. The PRB is 12 consecutive subcarriersin frequency domain and resources of one timeslot in time domain. Adefinition of the VRB is the same as a definition of the PRB duringcentralized resource allocation, and the VRB corresponds to the PRBduring distributed resource allocation. A PRB index is a PRB index, anda VRB index is a VRB index. Therefore, the PRB index may be differentfrom the VRB index. The RBG may include a plurality of PRBs, and aquantity of PRBs included in the RBG is determined based on bandwidth ofthe terminal, or is obtained based on an indication of a network device.The PRB index may be a PRB number, an RBG index may be an RBG number,the VRB index may be a VRB number, a subcarrier index may be asubcarrier number, and a subcarrier group index may be a subcarriergroup number. The subcarrier group includes at least one subcarrier.

FIG. 7 is a block diagram of a message sending apparatus according to anembodiment of the present invention. The message sending apparatus maybe implemented as all or a part of a terminal by using a dedicatedhardware circuit or a combination of software and hardware. The messagesending apparatus includes a receiving unit 720, a processing unit 740,and a sending unit 760.

The processing unit 740 is configured to obtain first configurationinformation, where the first configuration information is used fordetermining a first transmission resource pool.

The processing unit 740 is configured to determine the firsttransmission resource pool based on the first configuration information.

The processing unit 740 is configured to select a first transmissionresource from the first transmission resource pool in a firsttransmission resource obtaining manner when determining that a presetcondition is met.

The sending unit 760 is configured to send the V2X message by using thefirst transmission resource.

In an optional embodiment, the receiving unit 720 is configured toreceive RRC dedicated signaling sent by a first access network device;the processing unit 740 is configured to obtain cell handoverconfiguration information and first configuration information from theRRC dedicated signaling, where the cell handover configurationinformation and the first configuration information are configured by asecond access network device; and the processing unit 740 is furtherconfigured to hand over the apparatus from a source cell to a targetcell based on the cell handover configuration information.

The first access network device is an access network devicecorresponding to the source cell, and the second access network deviceis an access network device corresponding to the target cell.

Optionally, the preset condition includes a current moment belongs to ahandover time period, a start time of the handover time period is a timeat which the RRC dedicated signaling is received, and an end time of thehandover time period is a time at which the apparatus is handed over tothe target cell.

In another optional embodiment, the processing unit 740 is furtherconfigured to obtain second configuration information, where the secondconfiguration information is used for determining a second transmissionresource pool, a manner of obtaining a transmission resource from thesecond transmission resource pool is a second transmission resourceobtaining manner, and the second transmission resource obtaining manneris a transmission resource obtaining manner in which a transmissionresource is selected after channel sensing is performed for sensingduration T2; and the processing unit 740 is further configured todetermine the second transmission resource pool based on the secondconfiguration information.

Optionally, the preset condition includes at least one of the followingconditions: no valid sensing result is obtained from the secondtransmission resource pool; sensing duration in the second transmissionresource pool is less than T2; after the second configurationinformation is updated, sensing duration in the second transmissionresource pool is less than T2; synchronization between the apparatus andthe access network device becomes invalid; after a synchronizationsource is updated, sensing duration in the second transmission resourcepool is less than T2 based on a clock of an updated synchronizationsource; a difference between a time at which the V2X message isgenerated and a time at which the second configuration information isobtained is less than a preset threshold; or no transmission resource inan idle state is sensed in the second transmission resource pool.

In another optional embodiment, the processing unit 740 is furtherconfigured to: when obtaining a valid sensing result from the secondtransmission resource pool, obtain a second transmission resource fromthe second transmission resource pool in the second transmissionresource obtaining manner; and the sending unit 760 is furtherconfigured to send the V2X message by using the second transmissionresource.

In an optional embodiment, the first transmission resource pool and thesecond transmission resource pool are a same resource pool, and thefirst transmission resource obtaining manner is different from thesecond transmission resource obtaining manner.

In an optional embodiment, the processing unit 74 o is configured toobtain the preconfigured first configuration information; or thereceiving unit 720 is configured to receive radio resource control RRCdedicated signaling sent by the access network device, and theprocessing unit is configured to obtain the first configurationinformation from the RRC dedicated signaling; or the receiving unit 720is configured to receive system information sent by the access networkdevice, and the processing unit is configured to obtain the firstconfiguration information from the system information.

In an optional embodiment, the first transmission resource obtainingmanner includes any one of the following manners: a random selectionmanner; a manner in which a transmission resource is selected afterchannel sensing is performed for sensing duration T1, where the sensingduration T1 is less than a transmission delay value of the V2X message;or a carrier sense multiple access with collision avoidance CSMA/CAmanner.

For related details, refer to the method embodiment described in FIG. 2,FIG. 4, or FIG. 6.

It should be noted that the receiving unit 720 may be implemented by areceiver, or implemented by a combination of a processor and a receiver.The processing unit 720 may be implemented by a processor. The sendingunit 740 may be implemented by a transmitter, or implemented by acombination of a processor and a transmitter.

FIG. 8 is a block diagram of a message sending apparatus according toanother embodiment of the present invention. The message sendingapparatus may be implemented as all or a part of an access networkterminal or a first access network device by using a dedicated hardwarecircuit or a combination of software and hardware. The message sendingapparatus includes a sending unit 820, a processing unit 840, and areceiving unit 860.

The processing unit 840 is configured to generate first configurationinformation.

The sending unit 820 is configured to send the first configurationinformation to a terminal, where the first configuration information isused for determining a first transmission resource pool.

The terminal is configured to: determine the first transmission resourcepool based on the first configuration information; when determining thata preset condition is met, select a first transmission resource from thefirst transmission resource pool in a first transmission resourceobtaining manner; and send the V2X message by using the firsttransmission resource.

In an optional embodiment, the sending unit 820 is configured to: whencell handover needs to be performed on the terminal, send a handoverrequest message to a second access network device, where the secondaccess network device is an access network device corresponding to atarget cell; the receiving unit 86 o is configured to receive a handoveracknowledgement message sent by the second access network device, wherethe handover acknowledgement message includes cell handoverconfiguration information and the first configuration information; theprocessing unit 840 is configured to generate RRC dedicated signalingbased on the handover acknowledgement message; the sending unit 820 isconfigured to send the RRC dedicated signaling to the terminal, wherethe RRC dedicated signaling includes the cell handover configurationinformation and the first configuration information, and the terminal isconfigured to: be handed over from a source cell to the target cellbased on the cell handover configuration information, select the firsttransmission resource from the first transmission resource pool in thefirst transmission resource obtaining manner within a handover timeperiod, and send the V2X message by using the first transmissionresource.

In an optional embodiment, the processing unit 840 is configured togenerate second configuration information; the sending unit 820 isconfigured to send the second configuration information to the terminal,where the second configuration information is used for determining asecond transmission resource pool, a manner of obtaining a transmissionresource from the second transmission resource pool is a secondtransmission resource obtaining manner, and the second transmissionresource obtaining manner is a transmission resource obtaining manner inwhich a transmission resource is selected after channel sensing isperformed for sensing duration T2.

In an optional embodiment, the sending unit 820 is configured to sendradio resource control RRC dedicated signaling to the terminal, wherethe RRC dedicated signaling carries the first configuration information.Alternatively, the sending unit 820 is configured to send systeminformation to the terminal, where the system information carries thefirst configuration information.

For related details, refer to the method embodiment described in FIG. 4or FIG. 6.

It should be noted that the sending unit 820 may be implemented by atransmitter, or implemented by a combination of a processor and atransmitter. The processing unit 840 may be implemented by a processor.The receiving unit 86 o may be implemented by a receiver Rx, orimplemented by a combination of a processor and a receiver.

FIG. 9 is a block diagram of a message sending apparatus according toanother embodiment of the present invention. The message sendingapparatus may be implemented as all or a part of a second access networkdevice by using a dedicated hardware circuit or a combination ofsoftware and hardware. The message sending apparatus includes areceiving unit 920, a processing unit 940, and a sending unit 960.

The receiving unit 920 is configured to receive a handover requestmessage sent by a first access network device, where the handoverrequest message is sent by the first access network device when cellhandover needs to be performed on a terminal, and the first accessnetwork device is an access network device corresponding to a sourcecell.

The processing unit 940 is configured to generate a handover requestresponse message based on the handover request message.

The sending unit 960 is configured to send the handover request responsemessage to the first access network device, where the handover requestresponse message carries cell handover configuration information andfirst configuration information, and the first configuration informationis used for determining a first transmission resource pool.

The first access network device is configured to send radio resourcecontrol RRC dedicated signaling to the terminal, where the RRC dedicatedsignaling includes the cell handover configuration information and thefirst configuration information; and the terminal is configured to: behanded over from the source cell to a target cell based on the cellhandover configuration information, select a first transmission resourcefrom the first transmission resource pool in the first transmissionresource obtaining manner within a handover time period, and send theV2X message by using the first transmission resource.

In an optional embodiment, the first transmission resource obtainingmanner includes any one of the following manners: a random selectionmanner; a manner in which a transmission resource is selected afterchannel sensing is performed for sensing duration T1, where the sensingduration T1 is less than a transmission delay value of the V2X message;or a carrier sense multiple access with collision avoidance CSMA/CAmanner.

For related details, refer to the method embodiment described in FIG. 6.

It should be noted that the receiving unit 920 may be implemented by areceiver, or implemented by a combination of a processor and a receiver.The processing unit 940 may be implemented by a processor. The sendingunit 960 may be implemented by a transmitter, or implemented by acombination of a processor and a transmitter.

A person of ordinary skill in the art may understand that all or some ofthe steps of the embodiments may be implemented by hardware or a programinstructing related hardware. The program may be stored in acomputer-readable storage medium. The storage medium may include aread-only memory, a magnetic disk, an optical disc, or the like.

The foregoing descriptions are merely example embodiments of the presentinvention, but are not intended to limit the present invention. Anymodification, equivalent replacement, and improvement made withoutdeparting from the spirit and principle of the present invention shallfall within the protection scope of the present invention.

What is claimed is:
 1. A method comprising: obtaining, by a terminal,first configuration information, wherein the first configurationinformation is used for determining a first transmission resource poolthat is configured for vehicle to X (V2X) communications of theterminal; determining, by the terminal, the first transmission resourcepool based on the first configuration information; selecting, by theterminal, a first transmission resource from the first transmissionresource pool in a first transmission resource obtaining manner whendetermining that a preset condition is met, wherein the preset conditionis met when channel sensing performed on resources of a secondtransmission resource pool fails to produce a valid channel sensingresult within a time duration, the second transmission resource poolbeing configured for V2X communications of the terminal; and sending, bythe terminal, a V2X message by using the first transmission resource. 2.The method according to claim 1, wherein obtaining, by the terminal, thefirst configuration information comprises: receiving, by the terminal,radio resource control (RRC) dedicated signaling sent by a first accessnetwork device; and obtaining, by the terminal, cell handoverconfiguration information and the first configuration information fromthe RRC dedicated signaling, wherein the cell handover configurationinformation and the first configuration information are configured by asecond access network device; and wherein after obtaining, by theterminal, the first configuration information, the method furthercomprises: handing over the terminal from a source cell to a target cellbased on the cell handover configuration information, wherein: the firstaccess network device corresponds to the source cell, and the secondaccess network device corresponds to the target cell.
 3. The methodaccording to claim 1, wherein before selecting, by the terminal, thefirst transmission resource from the first transmission resource pool inthe first transmission resource obtaining manner when determining thatthe preset condition is met, the method further comprises: obtaining, bythe terminal, second configuration information, wherein the secondconfiguration information is used for determining the secondtransmission resource pool, a manner of obtaining a transmissionresource from the second transmission resource pool is a secondtransmission resource obtaining manner, and the second transmissionresource obtaining manner is a transmission resource obtaining manner inwhich a transmission resource is selected after channel sensing isperformed for sensing duration T2; and determining, by the terminal, thesecond transmission resource pool based on the second configurationinformation.
 4. The method according to claim 3, wherein the presetcondition comprises at least one of the following conditions: no validsensing result is obtained from sensing the second transmission resourcepool; sensing duration in the second transmission resource pool is lessthan T2; after the second configuration information is updated, sensingduration in the second transmission resource pool is less than T2;synchronization between the terminal and an access network devicebecomes invalid; after a synchronization source is updated, sensingduration in the second transmission resource pool is less than T2 basedon a clock of an updated synchronization source; a difference between atime at which the V2X message is generated and a time at which thesecond configuration information is obtained is less than a presetthreshold; or no transmission resource in an idle state is sensed in thesecond transmission resource pool.
 5. The method according to claim 3,wherein the method further comprises: when obtaining a valid sensingresult from sensing the second transmission resource pool, obtaining, bythe terminal, a second transmission resource from the secondtransmission resource pool in the second transmission resource obtainingmanner, and sending the V2X message by using the second transmissionresource.
 6. The method according to claim 1, wherein obtaining, by theterminal, the first configuration information comprises: obtaining, bythe terminal, the first configuration information that is preconfigured;or receiving, by the terminal, radio resource control (RRC) dedicatedsignaling sent by an access network device, and obtaining the firstconfiguration information from the RRC dedicated signaling; orreceiving, by the terminal, system information sent by the accessnetwork device, and obtaining the first configuration information fromthe system information.
 7. The method according to claim 1, wherein thefirst transmission resource obtaining manner comprises any one of thefollowing manners: a random selection manner; a manner in which atransmission resource is selected after channel sensing is performed forsensing duration T1, wherein the sensing duration T1 is less than atransmission delay value of the V2X message; or a carrier sense multipleaccess with collision avoidance (CSMA/CA) manner.
 8. A methodcomprising: sending, by an access network device, first configurationinformation to a terminal, wherein the first configuration informationis used for determining a first transmission resource pool that isconfigured for vehicle to X (V2X) communications of the terminal,wherein the first transmission resource pool is used for selecting, whena preset condition is met, a first transmission resource from the firsttransmission resource pool in a first transmission resource obtainingmanner for communicating a V2X message using the first transmissionresource, wherein the preset condition is met when channel sensing onresources of a second transmission resource pool fails to produce avalid channel sensing result within a time duration, the secondtransmission resource pool being configured for V2X communications ofthe terminal.
 9. The method according to claim 8, wherein the accessnetwork device is a first access network device, and the first accessnetwork device corresponds to a source cell; and sending, by the accessnetwork device, the first configuration information to the terminalcomprises: when cell handover needs to be performed on the terminal,sending, by the first access network device, a handover request messageto a second access network device, wherein the second access networkdevice corresponds to a target cell; receiving, by the first accessnetwork device, a handover acknowledgement message sent by the secondaccess network device, wherein the handover acknowledgement messagecomprises cell handover configuration information and the firstconfiguration information; and sending, by the first access networkdevice, radio resource control (RRC) dedicated signaling to theterminal, wherein the RRC dedicated signaling comprises the cellhandover configuration information and the first configurationinformation, and the cell handover configuration information is used forhanding over the terminal from the source cell to the target cell, andwherein the first transmission resource pool is used for selecting thefirst transmission resource from the first transmission resource pool inthe first transmission resource obtaining manner within a handover timeperiod for communicating the V2X message using the first transmissionresource.
 10. The method according to claim 8, wherein the methodfurther comprises: sending, by the access network device, secondconfiguration information to the terminal, wherein the secondconfiguration information is used for determining the secondtransmission resource pool, a manner of obtaining a transmissionresource from the second transmission resource pool is a secondtransmission resource obtaining manner, and the second transmissionresource obtaining manner is a transmission resource obtaining manner inwhich a transmission resource is selected after channel sensing isperformed for sensing duration T2.
 11. The method according to claim 8,wherein sending, by the access network device, the first configurationinformation to the terminal comprises: sending, by the access networkdevice, radio resource control (RRC) dedicated signaling to theterminal, wherein the RRC dedicated signaling carries the firstconfiguration information; or sending, by the access network device,system information to the terminal, wherein the system informationcarries the first configuration information.
 12. A method comprising:receiving, by a second access network device, a handover request messagesent by a first access network device, wherein the handover requestmessage is sent by the first access network device when cell handoverneeds to be performed on a terminal, the first access network devicecorresponds to a source cell, and the second access network devicecorresponds to a target cell; and sending, by the second access networkdevice, a handover request response message to the first access networkdevice, wherein the handover request response message carries cellhandover configuration information and first configuration information,and the first configuration information is used for determining a firsttransmission resource pool that is configured for vehicle to X (V2X)communications of the terminal; and wherein the cell handoverconfiguration information is used for handing over the terminal from thesource cell to the target cell, and wherein the first configurationinformation is used for selecting a first transmission resource from thefirst transmission resource pool in a first transmission resourceobtaining manner within a handover time period for communicating a V2Xmessage using the first transmission resource.
 13. The method accordingto claim 12, wherein the first transmission resource obtaining mannercomprises at least one of the following manners: a random selectionmanner; a manner in which a transmission resource is selected afterchannel sensing is performed for sensing duration T1, wherein thesensing duration T1 is less than a transmission delay value of the V2Xmessage; or a carrier sense multiple access with collision avoidance(CSMA/CA) manner.
 14. An apparatus comprising: a non-transitory memorystorage comprising instructions; and one or more processors incommunication with the memory storage, wherein the one or moreprocessors execute the instructions to: obtain first configurationinformation, wherein the first configuration information is used fordetermining a first transmission resource pool that is configured forvehicle to X (V2X) communications; determine the first transmissionresource pool based on the first configuration information; select afirst transmission resource from the first transmission resource pool ina first transmission resource obtaining manner when determining that apreset condition is met, wherein the preset condition is met whenchannel sensing performed on resources of a second transmission resourcepool fails to produce a valid channel sensing result within a timeduration, the second transmission resource pool being configured for V2Xcommunications; and send a V2X message by using the first transmissionresource.
 15. The apparatus according to claim 14, wherein the one ormore processors execute the instructions further to: receive radioresource control (RRC) dedicated signaling sent by a first accessnetwork device; obtain cell handover configuration information and thefirst configuration information from the RRC dedicated signaling,wherein the cell handover configuration information and the firstconfiguration information are configured by a second access networkdevice; and hand over the apparatus from a source cell to a target cellbased on the cell handover configuration information, wherein the firstaccess network device corresponds to the source cell, and the secondaccess network device corresponds to the target cell.
 16. The apparatusaccording to claim 15, the one or more processors execute theinstructions further to: when obtaining a valid sensing result fromsensing the second transmission resource pool, obtain a secondtransmission resource from the second transmission resource pool in asecond transmission resource obtaining manner; and send the V2X messageby using the second transmission resource.
 17. The apparatus accordingto claim 14, wherein the one or more processors execute the instructionsfurther to: obtain second configuration information, wherein the secondconfiguration information is used for determining the secondtransmission resource pool, a manner of obtaining a transmissionresource from the second transmission resource pool is a secondtransmission resource obtaining manner, and the second transmissionresource obtaining manner is a transmission resource obtaining manner inwhich a transmission resource is selected after channel sensing isperformed for sensing duration T2; and determine the second transmissionresource pool based on the second configuration information.
 18. Theapparatus according to claim 17, wherein the preset condition comprisesat least one of the following conditions: no valid sensing result isobtained from sensing the second transmission resource pool; sensingduration in the second transmission resource pool is less than T2; afterthe second configuration information is updated, sensing duration in thesecond transmission resource pool is less than T2; synchronizationbetween the apparatus and an access network device becomes invalid;after a synchronization source is updated, sensing duration in thesecond transmission resource pool is less than T2 based on a clock of anupdated synchronization source; a difference between a time at which theV2X message is generated and a time at which the second configurationinformation is obtained is less than a preset threshold; or notransmission resource in an idle state is sensed in the secondtransmission resource pool.
 19. The apparatus according to claim 14,wherein the one or more processors execute the instructions further to:obtain the first configuration information that is preconfigured; orreceive radio resource control (RRC) dedicated signaling sent by anaccess network device, and obtain the first configuration informationfrom the RRC dedicated signaling; or receive system information sent bythe access network device, and obtain the first configurationinformation from the system information.
 20. The apparatus according toclaim 14, wherein the first transmission resource obtaining mannercomprises any one of the following manners: a random selection manner; amanner in which a transmission resource is selected after channelsensing is performed for sensing duration T1, wherein the sensingduration T1 is less than a transmission delay value of the V2X message;or a carrier sense multiple access with collision avoidance (CSMA/CA)manner.
 21. An apparatus, comprising: a non-transitory memory storagecomprising instructions; and one or more processors in communicationwith the memory storage, wherein the one or more processors execute theinstructions to: send first configuration information to a terminal,wherein the first configuration information is used for determining afirst transmission resource pool that is configured for vehicle to X(V2X) communications of the terminal, wherein the first transmissionresource pool is used for selecting, when a preset condition is met, afirst transmission resource from the first transmission resource pool ina first transmission resource obtaining manner for communicating a V2Xmessage using the first transmission resource, wherein the presetcondition is met when channel sensing on resources of a secondtransmission resource pool fails to produce a valid channel sensingresult within a time duration, the second transmission resource poolbeing configured for V2X communications of the terminal.
 22. Theapparatus according to claim 21, wherein the one or more processorsexecute the instructions further to: when cell handover needs to beperformed on the terminal, send a handover request message to a secondaccess network device, wherein the second access network devicecorresponds to a target cell; receive a handover acknowledgement messagesent by the second access network device, wherein the handoveracknowledgement message comprises cell handover configurationinformation and the first configuration information; and send radioresource control (RRC) dedicated signaling to the terminal, wherein theRRC dedicated signaling comprises the cell handover configurationinformation and the first configuration information, and the cellhandover configuration information is used for handing over the terminalfrom a source cell to the target cell, and wherein the firsttransmission resource pool is used for selecting the first transmissionresource from the first transmission resource pool in the firsttransmission resource obtaining manner within a handover time period forcommunicating the V2X message using the first transmission resource. 23.The apparatus according to claim 21, wherein the one or more processorsexecute the instructions further to: send second configurationinformation to the terminal, wherein the second configurationinformation is used for determining the second transmission resourcepool, a manner of obtaining a transmission resource from the secondtransmission resource pool is a second transmission resource obtainingmanner, and the second transmission resource obtaining manner is atransmission resource obtaining manner in which a transmission resourceis selected after channel sensing is performed for sensing duration T2.24. The apparatus according to claim 21, wherein the one or moreprocessors execute the instructions further to: send radio resourcecontrol (RRC) dedicated signaling to the terminal, wherein the RRCdedicated signaling carries the first configuration information; or sendsystem information to the terminal, wherein the system informationcarries the first configuration information.
 25. A apparatus comprising:a non-transitory memory storage comprising instructions; and one or moreprocessors in communication with the memory storage, wherein the one ormore processors execute the instructions to: receive a handover requestmessage sent by a first access network device, wherein the handoverrequest message is sent by the first access network device when cellhandover needs to be performed on a terminal, and the first accessnetwork device corresponds to a source cell; and send a handover requestresponse message to the first access network device, wherein thehandover request response message carries cell handover configurationinformation and first configuration information; and wherein the cellhandover configuration information is used for handing over the terminalfrom the source cell to a target cell, and wherein the firstconfiguration information is used for selecting a first transmissionresource from a first transmission resource pool in a first transmissionresource obtaining manner within a handover time period forcommunicating a V2X message using the first transmission resource. 26.The apparatus according to claim 25, wherein the first transmissionresource obtaining manner comprises any one of the following manners: arandom selection manner; a manner in which a transmission resource isselected after channel sensing is performed for sensing duration T1,wherein the sensing duration T1 is less than a transmission delay valueof the V2X message; or a carrier sense multiple access with collisionavoidance (CSMA/CA) manner.